| Straw returning to the field is an important agronomic measure,which can provide rich nutrients to the soil,promote the growth and reproduction of soil microorganisms,and thus affect the production of greenhouse gases and the mineralization of organic matter in the soil.Aggregates can protect organic matter in soil.The protective effect of organic matter was significantly different in different aggregates.The mineralization of organic matter in different aggregates may be different after straw addition,which will further affect the C and N cycling in soil,thus affecting the greenhouse gas emissions.In order to investigate the effects of straw on greenhouse gas emission and DOC composition,we selected the red paddy soil and five soils with different organic matter content as the research objects.The experiment was conducted in the design room to study the effects of straw addition.Greenhouse gas emission test and characterization of soil soluble organic carbon(DOC)components.The main findings are as follows:(1)Straw addition significantly increased the emission fluxes and cumulative emissions of CH4 and CO2,thus significantly inhibited the emission of N2O.The correlation analysis showed that the emission fluxes of CH4 and CO2 were positively correlated with DOC in soil,but negatively correlated with the concentrations of NO3'-N and WEN in soil.However,the emission flux of N2O was positively correlated with WEN concentration,and negatively correlated with the concentration of NH4+-N and NO3--N in soil.DOC and NO3--N had the greatest effect on the emission of CH4 CO2 and N2O in soil.The addition of high C/N straw stimulated the activity of microorganism in soil,produced the stimulation effect,and increased the concentration of DOC and mineral nitrogen in the mineralization of soil original organic matter.(2)By screening characteristic wavenumber variables and using partial least square regression method,a model for characterization of soil soluble organic carbon by infrared spectroscopy can be established.The results showed that there was an intrinsic relationship between the absorption of infrared spectrum and the concentration of soil dissolved organic carbon.The determination coefficient of soil dissolved organic carbon model obtained by mid-infrared spectroscopy combined with partial least square regression can reach 0.966.(3)The characteristic fluorescence spectrum parameters of DOC obtained by three dimensional fluorescence spectroscopy including fluorescence index(FII),humification index(HI),autogenetic index(BIX)and so on,all indicated that the main sources of DOC in the soil in this experiment were microbes.Under the experimental conditions,the components of DOC showed dynamic changes with the increase of culture time.It may be related to the early and middle stage of straw degradation,the activity of microbial life is very active and the carbohydrate in Dom is easy to degrade,and the consumption rate of protein-like substances is faster.Tyrosine and humic acid account for a large proportion of the five components,and the proportion of changes in the culture process is also relatively large.Straw promoted the accumulation of humic acid,aromatic protein ? and fulvic acid to a great extent,and also promoted the degradation of metabolites and aromatic protein ?. |
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